Unit-distance encoder



U.S. Cl. 340-347 8 Claims ABSTRACT OF THE DISCLOSURE A unit-distance encoder in which all transfer points between counts are controlled by segments mounted on the two outermost tracks of greatest diameter and circumferential length.

SUMMARY OF THE INVENTION One object of my invention is to provide a unit-distance encoder of high accuracy.

Another object of my invention is to provide a unitdistance encoder in which transfer points for all counts are controlled on the two outermost tracks of greatest diameter.

A further object of my invention is to provide a multiple-pattern unit-distance encoder of simple construction which eliminates inaccuracies due to backlash in reduction gearing without requiring auxiliary electronic components.

A still further object of my invention is to provide a multiple-pattern unit-distance encoder of truncated count wherein a plurality of digits may change polarity simultaneously at the recycling transfer point.

Other and further objects of my invention will appear from the following description.

DESCRIPTION OF THE DRAWINGS In the accompanying drawings which form part of the instant specification and are to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views:

FIG. l is a developed schematic view showing the pattern and `brush arrangement for the high-speed disc.

FIG. la is a diagrammatic view showing the outputs provided by the high-speed pattern of FIG. 1.

FIG. 2 is a developed schematic view showing the pattern and brush interconnections for the truncated lowspeed disc.

FIG. 2a is a diagrammatic View to be read in conjunction with FIG. 2 showing the X and Y outputs of the high-speed disc of FIG. 1.

FIG. 2b is a diagrammatic view showing the outputs provided by the low-speed pattern of FIG. 2.

FIG. 3 is a sectional elevation of my two-speed encoder.

FIG. 4 is a schematic view showing the interconnections between the high-speed and low-speed pattern discs.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1a of the drawings, the highspeed pattern provides sixteen counts ranging from through in the `Gray code. Three digits are generated.

The least significant digit is provided by the segments A; the digit of intermediate significance, by the segments B; and the most significant digit, by the segment C. It is desired to provide an A output during the 1 and 2 intervals, the 5 and 6 intervals, the 9 and 1t)` intervals, and the 13 and 14 intervals. It is desired to provide a B output during the 2 through 5 intervals and the 1t]` through 13 intervals. It is desired to provide a C output during United States Patent O 3,548,397 Patented Dec. 15, 1970 ICC the 4 through 1.1 intervals. It is also desired to provide X and Y outputs for eliminating ambiguities in the lowspeed pattern. An X output is provided during the 0 through 3 and the 8 through 11 intervals; and a Y output is provided during the 4 through 7 and 12 through 15 intervals.

Referring now to FIG. l, the high-speed pattern is shown broken at the 15-0 transfer point and developed. 'Ihe high-speed disc 10 comprises eight circles of segments indicated generally by the reference numerals 11 through 18. The two outermost circles or tracks comprise 11 and 12. In track 11, an X segment subtends the 0 interval; a B segment, the 2 interval; a C segment, the 4 interval; a B segment, the 5 interval; a Y segment, the 7 interval; and A segments subtend the 9 and 10` and 13 and 14 intervals. In track 12, A segments subtend the 1 and 2 and the 5 and 6 intervals; an X segment subtends the 8 interval; a B segment, the 10 interval; a C segment, the 11 interval; a B segment, the 13 interval; and a Y segment, the 15 interval. In track 11, the C and B segments adjacent the 4-5 transfer point are provided with a somewhat enlarged insulating space; and in track 12 the B and C segments adjacent the 10-11 transfer point are similarly provided with an enlarged insulating space. The purpose of this is to prevent shortcircuiting between the B and C segments due to deposition in the insulating gap of minute particles occasioned by brush wear.

Track 13 comprises B segments extending from the midpoint of the 2 interval to the midpoint of the 5 interval and from the midpoint of the 10 interval to the midpoint of the 13 interval. Track 14 comprises a C segment extending from the midpoint of the 4 interval to the midpoint of the 11 interval. Track 15 comprises X segments extending from the midpoint of the 0 interval to the 3-4 transfer point and from the midpoint of the 8 interval to the |11-12 transfer point. Track 16 comprises Y segments extending from the 3-4 transfer point to the midpoint of the 7 interval and from the 11-12 transfer point to the midpoint of the 15 interval. Tracks 17 and 18 comprise a double-width continuous Z slip ring which affords a common connection for the application of input excitation voltage. The high-speed disc comprises a multiplicity of layers. The pattern at the surface is shown in FIG. 1. All segments of the same type are electrically connected through risers which extend from the underlying layers to the surface segments shown. The remaining portion of the surface comprises electrical insulation.

A column of eight aligned brushes is indicated generally by the reference numeral 20; and one brush engages each track. Two brushes engage the double-width Z slip ring in tracks 17 and 18 in order to reduce electrical wear by decreasing the current flow. All 'eight brushes 20 are shorted together.

The encoder is shown at the midpoint of the 3 interval. As the brushes move to the right relative to the stationary pattern, the 34 transfer point is created by the brush of track 11 contacting a C segment. At the midpoint of the 4 interval, the brush of track 14 contacts a C segment, thus insuring the continued existence of a C output. Slightly before the 4-5 transfer point, the brush of track 11 disengages a C segment; but a C output is produced because the brush of track 14 is well in engagement with a C segment. At the 4-5 transfer point, the brush of track 12 engages an A segment, thus providing the desired A output. Slightly after the 4-5 transfer point, the brush of track 11 engages a B segment, thus insuring the presence of a B output produced by the engagement of the brush of track 13 with a B segment. At the midpoint of the 5 interval, the brush of track 13 disengages a B segment; however, a B output is still produced from track 11. At the 5-6 transfer point, the brush of track 11 disengages its B segment. At the 6-7 transfer point, the

brush of track 12 disengages its A segment. Also adjacent the 6-7 transfer point, the brush of track 11 engages a Y segment, thus insuring the presence of a Y output produced by the engagement of the brush of track 16 with a Y segment. At the midpoint of the 7 interval, the brush of track 16 disengages its Y segment; however, a Y output is still produced by track 11. At the 7-8 transfer point, the brush of track 11 disengages its Y segment; and the brush of track 12 engages its X segment.

At the midpoint of the 8 interval, the brush of track 15 engages an X segment, thus insuring the presence of an X output. At the 8 9 transfer point, the brush of track 11 engages an A segment. Also adjacent the 8-9 transfer point, the brush of track 12 disengages its X segment; however, an X output is still produced since the brush of track 15 is well in engagement with its X segment.

It will be noted that a B output is provided by track 12 in the first half of the interval, by both tracks 12 and 13 during the last half of the 10 interval, by track 13 during the 11 and 12 intervals, by both tracks 12 and 13 during the first half of the 13 interval, and by track 12 during the last half of the 13 interval. Thus track 12 is effectively in control of the origination of a B output at the 9-10 transfer point and of the termination of a B output at the 13-14 transfer point. Track 11 is in control of the origination of a B Output at the 1-2 transfer point and of the termination of a B output at the 5-6 transfer point. Track 11 controls the origination of a C output at the 3-4 transfer point; and track 12 controls the termination of a C output at the 11412 transfer point.

As previously indicated, the X and Y outputs are used for controlling the low-speed pattern in order to eliminate amibigities. Only the ends of the X and Y segments adjacent the 15-0 and 7-8 transfer points are critical. Accordingly, the X and Y segments of tracks 15 and 16 are shortened adjacent these transfer points and then effectively lengthened by the overlapping X and Y segments of tracks 11 and 12. 'Since the X and Y segments are not critical adjacent the 3-4 and 11-12 transfer points, the segments of tracks 15 and 16 are made substantially to coincide with these points.

Referring now to FIG. 2a, there is shown the region of X and Y outputs of the high-speed pattern of FIG. 1 for a multiple-pattern encoder having a maximum count of forty-eight ranging from 0 through 47, wherein the low-speed pattern revolves through one revolution while the high-speed pattern rotates through three revolutions.

Referring now to FIG. 2b, the low-speed pattern provides six counts in increments of eight comprising 0, 8,

16, 24, 32, and 40. Three digits are generated. The least significant digit is provided by the segments D, the digit of intermediate significance by the segment E, and the most significant digit by the segment F. It is desired to provide a 4D output during the 8 through 23 intervals and the 40 through 47 intervals. It is desired to provide an E output during the 16 through 47 intervals; and an F output during the 32 through 47 intervals. It will be noted that the count of the low-speed pattern is truncated, since it is not an integral power of the number 2. Accordingly the D, E, and F outputs all change polarity at the 47-0 recycling transfer point.

Referring now to FIG. 2, the low-speed pattern is shown broken at the 47-0 recycling transfer point and developed. The low-speed disc 50 comprises nine circles of segments indicated generally by the reference numerals 51 through 59. The two outermost circles or tracks comprise S1 and 52. In track 51, a D segment subtends the 6 through 11 intervals; and E segment, the 14 through 19 intervals; and F segment, the 30 through 35 intervals; and a D segment, the 38 through 43 intervals. `In track 52, a D segment subtends the 20 through 25 intervals; and a W segment, the 44 through 1 intervals.

Track 53 comprises D segments subtending the 10 through 21 intervals and the 42 through 1 intervals. Track 54 comprises an E segment subtending the 18 through 1 intervals; and track S5 comprises an F segment subtending the 34 through 1 intervals. Track 56 comprises a Z segment subtending the 6 through 45 intervals and a W segment extending approximately from the midpoint of the 46 interval to the 1-2 transfer point. Track 57 comprises a Z segment extending from the 5-6 transfer point to approximately the midpoint of the 43 interval and a W segment subtending the 44 through 1 intervals. The somewhat enlarged insulating spaces of track 56 adjacent the -46 transfer point and of track 57 adjacent the 43-44 transfer point are provided to prevent short-circuiting between the Z and W segments due to deposition in the insulating material of minute particles occasioned by brush wear. Track 58 comprises a continuous X slip ring, and track 59 comprises a continuous Y slip ring. The lowspeed disc comprises a multiplicity of layers. The surface pattern is shown in FIG. 2. Similar segments are connected by risers which extend from underlying layers to the surface segments.

A colum of nine brushes is indicated generally by the reference numeral 60, one brush being associated with each track. The brush of track 58 is connected to the brush of track 51; the brush of track 59 is connected to the brush of track 52; and the brushes of tracks 53 through 57 are shorted together.

The composite encoder is shown at the midpoint of the 27 interval. As the brushes 60 move to the right relative to the stationary pattern, the brush of track 51 engages an F segment at the 29-30 transfer point. However, no F output is produced since the brushes of tracks 51 and 58 receive no excitation from the X slip ring. At the 3132 transfer point, the X slip ring of track 58 receives excitation from the high-speed pattern; and the low-speed pattern now provides an F output, since the brush of track 51 is well in engagement with its F segment. At the 33-34 transfer point, the brush of track engages the F segment, thus insuring the continued existence of an F output. Adjacent the 35-36 transfer point, the brush of track 51 disengages its F segment, and the excitation of the X slip ring 58 is removed; however, an F output is produced because the brush of track 5S is well in engagement with the F segment. The D output is similarly initiated in track 51 at the 39-40 transfer point and reinforced in track S3 at the 41-42 transfer point.

Slightly before the 4344 transfer point or approximately at the midpoint of the 43 interval, the brush of track 57 disengages its Z segment and enters the somewhat extended insulating space. However, the brush of track 56 is still in engagement with its Z segment, so that the brushes of tracks 53 through 55 continue to receive input excitation voltage. At the 32-44 transfer point, the brushes of tracks 52 and 57 enagge their W segments; and the brush of track 52 is excited by Y slip ring 59. Accordingly, the brush of track 57 again receives input excitation voltage reinforcing that supplied from the brush of track 56. The brush of track 56 disengages its Z segment at the 4S-46 transfer point. But the brush of track 57 supplies excitation to the brushes of tracks 53 through 55. At the midpoint of the 46 interval, the brush of track 56 engages its W segment, thus reinforcing that supplied from the brush of track 57.

At the 47-0 recycling transfer point, the Y output of the high-speed pattern is terminated; and no excitation is applied to Y slip ring 59. This removes the excitation of the W segments of tracks 5 2, 56, and 57. Since the brushes of both tracks S6 and 57 are in engagement with W segments, the excitation of the brushes of tracks 53, 54, and 55 is similarly removed. Thus the D, E, and F outputs are terminated simultaneously.

At the 1-2 transfer point, the brushes of tracks 52 through 57 disengage their associated segments. At the 5 6 transfer point7 the brush of track 51 engages a D segment and the brushes of tracks 56 and 57 engage Z segments; however, no D output is produced, since the X slip ring of track 58 receives no excitation. The D output is initiated at the 7-8 transfer point when the X slip ring is excited. This 'D output is reinforced in track 53 at the 9-10 transfer point, since the brushes of tracks 56 and 57 are well in engagement with the Z segments.

An E output is similarly initiated in track 51 at the -16 transfer point and reinforced in track 54 at the 17-18 transfer point.

At the 19-20 transfer point, the brush of track 52 engages a D segment; and the Y slip ring is excited, thus reinforcing the D output provided by track 53. At the 21-22 transfer point, the brush of track 53 disengages its D segment. However a D output is still produced, because the brush of track 52 engages a D segment and receives excitation from the Y slip ring 59. At the 23-24 transfer point, the excitation of the Y slip ring is removed, and the D output is terminated.

It will be noted that the leading edges of the D, E, and F outputs are created by segments in track 51; and the trailing edges thereof are generated by the segments in track S2. The W segment of track 52 generates the simultaneous trailing edges of the D, E, and F outputs at the recycling transfer point.

For the high-speed pattern of FIG. 1, the tolerances in positioning the ends of the segments of the non-critical tracks 13, 14, 15, and 16 are approximately itl/2 interval. F or the low-speed pattern of FIG. 2, the tolerance in positioning the segments of tracks 51 through 57 is approximately i2 intervals including backlash in the gear trains connecting the high-speed and low-speed brush assemblies and 60. All transfer points for the low-speed pattern are controlled by the segments mounted on the -two outermost tracks 51 and 52, the brushes of which are controlled 'by the X and Y outputs of the high-speed pattern of FIG. 1.

Referring now to FIG. 3, the eight high-speed brushes 20 are secured to a brush holder 21 which is mounted on a high-speed input shaft 24. Input shaft 24 is journalled in a bearing 23 mounted in an end wall 22 and in another bearing which is mounted in a hanger 31. The high-speed brush assembly is statically and dynamically balanced by a counterweight 2S. The high-speed shaft 24 drives a countershaft 33 through a gear reduction indicated generally by the reference numeral 32 which comprises a pinion mounted on shaft 24 and a gear mounted on counttershaft 33. Countershaft 33 is supported in bearings mounted in hanger 31 and in another hanger 35. Countershaft 33 drives the low-speed shaft 64 through reduction gearing indicated generally by the reference numeral 34 and comprising a pinion mounted on countershaft 33 and a gear mounted on low-speed shaft 64. The speed reduction provided by 32 is 2:1; and the speed reduction provided by 34 is 1.5: l. Thus the overall speed reduction between the high-speed and low-speed shafts 24 and 64 is 3:1. The low-speed shaft 64 is journalled in a bearing 63 mounted in a second end wall 62 and in a bearing mounted in hanger 3S. The nine low-speed brushes 60 are secured to a brush holder 61 which is mounted on lowspeed shaft 64 and provided with a balancing counterweight 65- End walls 22 and 62 are secured to a cylindrical housing 36 which encloses the encoder. The highspeed pattern 10 is secured to end wall 22, and the lowspeed pattern 50 is secured to end wall 62.

Referring now to FIG. 4, a source of input excitation voltage, which is shown as being positive, is coupled to the Z segments of patterns 10 and 50. The X and Y output segments of the high-speed pattern 10 are connected to the respective X and Y input segments of the lowspeed pattern 50. Pattern 10 provides A, B, and C outputs from its corresponding segments; and pattern 50 provides D, E, and F outputs from its corresponding segments. The W segments of the low-speed pattern are provided only with internal connections and are not used externally.

It will be seen that I have accomplished the objects of my invention. All transfer points are generated by segments mounted on the two outermost tracks of the highspeed disc. My unit-distance encoder accordingly has a high accuracy, since the two outermost tracks have the greatest circumferential length. The transfer points for the low-speed pattern are controlled by segments mounted on the two outermost tracks. This also affords an increase in the permissible tolerances. I have provided a multiple-pattern encoder of truncated count, wherein a plurality of digits change polarity at the recycling transfer point by utilizing auxiliary internally-connected segments which interrupt the input excitation voltage at the recycling transfer point.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of my claims. It is further obvious that various changes may be made in details within the scope of my claims Without departing from the spirit of my invention. It is, therefore, to be understood that my invention is not to be limited to the specific details shown and described.

Having thus described my invention, what I claim is:

1. A unit-distance encoder of truncated count having a recycling transfer point at which a plurality of digits change polarity including in combination a plurality of concentric circles of segments providing a plurality of output digits, a further concentric circle having a substantially continuous slip ring which is interrupted for a short interval adjacent the recycling transfer point, and means including the further circle for exciting at least two circles of the plurality.

2. An encoder as in claim 1 in which the plurality of circles comprises a pair of outermost circles and at least two additional circles, in which the exciting means further includes a rst short segment occupying a portion of the interrupted interval of the slip ring and a second short segment mounted on one of the pair of outermost circles and positioned adjacent the recycling transfer point, and in -which the exciting means excites the additional circles.

3. A multiple-pattern unit-distance encoder including in combination on a high-speed pattern providing a pair of substantially complementary signals which change polarity at substantially intervals, a low-speed pattern comprising at least three concentric circles of segments providing at least two output digits, means responsive to the pair of complementary signals for exciting the two outermost circles of the low-speed pattern, means comprising a first segment of one of the excited circles for initiating a first output digit, means comprising a second segment of said one of the excited circles for initiating a second output digit, means comprising a third segment of the other of the excited circles for terminatingI the `first output digit, means comprising a fourth segment of said other of the excited circles for terminating the second output digit, means comprising a fth segment of the third circle of the low-speed pattern for continuing the first output digit subsequent to initiation and prior to termination, means comprising a sixth segment of a circle of the low-speed pattern other than the two outermost for continuing the second output digit subsequent to initiation and prior to termination, means directly connecting the rst and third and fifth segments, and means directly connecting the second and fourth and sixth segments.

4. A unit-distance encoder including in combination at least three concentric circles of segments providing at least three output digits, means comprising -rst segments of at least one of the two outermost circles for generating a first output digit of highest periodicity, means comprising second segments of at least one of the two outermost circles for initiating and terminating a second output digit of lower periodicity, means comprising third segments of at least one of the two outermost circles for initiating and terminating a third output digit of lower periodicity, means comprising a fourth segment of the third circle for continuing the second output digit subsequent to initiation and prior to termination, means comprising a iifth segment of a circle other than the two outermost for continuing the third output digit subsequent to initiation and prior to termination, means directly connecting the fourth segment and the second segments, and means directly connecting the fth segment and the third segments.

5. An encoder as in claim 4 in which each initiating and terminating segment overlaps its associated continuation segment by not appreciably less than one-half the interval of one count.

6. An encoder as in claim 4 wherein the circles of segments are mounted on a stationary multiple-layer disc having a surface which is contacted by rotating brushes.

7. An encoder as in claim 3 in ywhich each initiating 8 and terminating segment overlaps its associated continuation segment by an amount which corresponds to approximately 45 of the high-speed pattern.

8. An encoder as in claim 3 wherein the circles of segments are mounted on a stationary multiple-layer disc having a surface which is contacted by rotating brushes.

References Cited UNITED STATES PATENTS 3,054,996 9/1962 Spaulding 340-347 3,197,763 7/1965 Fisher 340-347 3,286,251 ll/1966 Bynn 340-347 3,425,052 1/1969 Jones 340-347 MAYNARD R. WILBUR, Primary Examiner J. GLASSMAN, Assistant Examiner 

